Tannic acid (CAS 1401-55-4): storage and disposal

Serious eye irritation is what decides handling, so the lid should stay on firmly to keep dust out of the air, and the tub should not sit on a high shelf. Keep it in a dry, labelled, well organised store, dated on arrival, and apart from food grade supplies. Iron salts are the practical thing to separate, because tannic acid stains blue-black on contact with iron, so spilt powder near iron(II) or iron(III) stock can mark the shelf. Light and air darken it, so a window shelf is a poor place. Histology stores should keep it in its labelled container.

Pale yellow-brown powder is normal, and the first change to look for is darkening. Tannic acid is oxidised by air and light, so an old tub goes darker, and a tub that has taken up damp may clump or set. Blue-black marks on a shelf or a lid point to contact with iron. Also check for a loose or cracked lid, powder on the outside, a faded label and an unknown date of receipt. A tub that has darkened, caked or stained its shelf is still the same chemical waste, and should stay closed and be listed for collection.

We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a general laboratory pack with compatible chemicals.

A bin or a skip is not the place for it, and it must never go into a sink or drain, where it would stain. It must not be dissolved or neutralised first either. Tannic acid is organic, so a discarded tub outside a lab pack usually takes 16 05 08*, and 18 01 06* usually applies in a healthcare setting such as a histology department, and the producer confirms the classification. Record the colour of the powder, the amount left and whether the lid has failed. The collector groups it with other organic solids and keeps it away from iron salts, which is why those should be itemised separately on your inventory.

Usually held as: solid.

Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.